Test & Tune

[bigriggr]

My Garmin GPS is recording 70.6 mph in heat trim. Does this speed sound about right or is there more to be had? Setup specs: Eagle SGX MAC 67, bar stock AB67 set at 10 3/4", negative 1 1/4 degree strut, H-38 w/5.29 cup, front sponson attack angles L-2.30 R-2.40, 50% red max probably 4 gallons run thru, engine temp seems to be only around 140 degrees. The boat does seem to run pretty wet. If you think the speed is down can I hear some tuning sugestions?

Thanks,

 

[aaron alberico]

Speed is a little down,

i would think around 80mph is where you should be,

i'm running same boat and mod mac67, on 60%nitro, pipe about 10in, h32

regards Aaron

 

[Chris Wood]

sounds like the front sponsons are two tight..

my suggestion is this. first i don't like digital levels.

i would take all the shims out of the rear tube. run it.. boat should be light on the front end. then start shiming the rear tube till the boat does not dance.. may have to tighten the boat up for racing

you can also put more strut angle in it and that will plant the nose and give better launch.

my 60 boat runs 85-87 pipe @ 11" with a h-32 cmb green head and big belly cmb pipe.

chris

 

[bigriggr]

Thanks Aaron and Chris. I picked a bad day to test, the water was like glass. Took shim's out of rear sponson tubes and worked the pipe in from 10 3/4 to 10 1/4 and gained 3 mph. But the conditions were very wet. Will look for a day with wind like it so often is when your running heats.

Thanks guys I'll keep testing with your advice,

 

[shoboat]

Big Rigger,

Try an H-32 and I think you will be happier.

Have Fun Testing,

Mark Sholund

 

[AndyBrown]

Big Rigger,
Try an H-32 and I think you will be happier.

Have Fun Testing,

Mark Sholund

Mark,

We run in the high 80's with the H-38 4.8" cup.

From all of our testing the H-38 is faster on the SGX. The H-32 was faster on the SG.

Big Rigger,

Shorten the pipe about 1/4" and see what happens. It may seem wet because it is only running 70 - 73.

Make sure your sponson bottoms are sharp. Block sand them if needed.

 

[shoboat]

Andy,

I just go by the propellers that are ordered the most. On My SG you are right, it liked the 32

better. I think most are still running too much cup on the 38 so it loads the motor too much.

Most 38's have 5.29" of cup stock,so if you back them down to 4.74" it will unload more.

Good Luck Testing,

Mark Sholund

 

[bigriggr]

Made some big improvements. Sharpened the sponsons, pulled the pipe in to 10 1/8" and removed the rear tube shims. THAT put some air underneath. Hopped here and again down the straights during heats, but still handled awesome in light windy conditions. Although the element looked pretty twisted up and pulled out. Too rich or too lean? Took first in two heats and starter belt snapped on the third. Had a blast!!! Did not have the gps in the hull but I was told by fellow boaters I was very close to 80mph. I'll get with shoboat on another H-38. Haven't received a prop from the ladies at cmdi yet. Am I looking for a 6535A or 6535B?

Anyway, Thanks again boaters

 

[Buckshot]

Where are you measuring to on the AB .67 Bar Stock pipe? I set mine at 11.25" from the center of the M on the side of the case to the third threaded seam(center of the pipe). Boat ran ok first time out but didn't want to push a brand new motor right out of the gate.

Running H-38 @ 5.1"

Regards,

-Buck-

 

[bigriggr]

Where are you measuring to on the AB .67 Bar Stock pipe? I set mine at 11.25" from the center of the M on the side of the case to the third threaded seam(center of the pipe). Boat ran ok first time out but didn't want to push a brand new motor right out of the gate.Running H-38 @ 5.1"

Regards,

-Buck-

Buck

Yes, third seam as you called it, widest diameter of the pipe. Ran the tape along the center of the pipe and measured to the centerline of the engine.

Ran 10 3/4" all year until I was advised this boat should run faster. And it does!!!!!!

 

[Buckshot]

Where are you measuring to on the AB .67 Bar Stock pipe? I set mine at 11.25" from the center of the M on the side of the case to the third threaded seam(center of the pipe). Boat ran ok first time out but didn't want to push a brand new motor right out of the gate.Running H-38 @ 5.1"

Regards,

-Buck-

Buck

Yes, third seam as you called it, widest diameter of the pipe. Ran the tape along the center of the pipe and measured to the centerline of the engine.

Ran 10 3/4" all year until I was advised this boat should run faster. And it does!!!!!!

Thank You

-Buck-